1. Consider the following recursive function: def mystery (a, b): if b == 0: return 0 else: return a + mystery (a, b-1) (a) Draw a diagram showing the order of calls made by mystery (2, 5) and show the Return values for each call. (b) What value will be returned by mystery (2,5)? (c) How many levels are in the call tree if a=n2(n square)?, b=n? (d) What is the running time of mystery (a, b) if a=n2(n square)?, b=n?